US4158031A - Electrically conductive foam mouldings - Google Patents

Electrically conductive foam mouldings Download PDF

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Publication number
US4158031A
US4158031A US05/782,074 US78207477A US4158031A US 4158031 A US4158031 A US 4158031A US 78207477 A US78207477 A US 78207477A US 4158031 A US4158031 A US 4158031A
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US
United States
Prior art keywords
particles
polystyrene
electrically conductive
beads
mold
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US05/782,074
Inventor
Franz G. Reuter
Tankred Menzel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Reuter Technologie GmbH
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Reuter Technologie GmbH
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Filing date
Publication date
Priority to DE2617698 priority Critical
Priority to DE19762617698 priority patent/DE2617698A1/en
Application filed by Reuter Technologie GmbH filed Critical Reuter Technologie GmbH
Application granted granted Critical
Publication of US4158031A publication Critical patent/US4158031A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B65CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65DCONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D81/00Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents

Abstract

This invention relates to electrically conductive foam moulding manufactures from electrically conductive polystyrene beads containing blowing agent.

Description

The present invention relates to electrically conductive foam mouldings of polystyrene, their use and a process for the manufacture of these foam mouldings.

It is known to employ polystyrene foams, which are manufactured from polystyrene beads containing blowing agent (the beads being commercially available under the name "Styropor") on an extensive scale as packaging materials. However, for numerous fields of packaging these foam plastics cannot be used, since they generate, or carry, substantial electrostatic charges. For this reason, numerous materials such as MOS electronic circuits, explosives, plastic lenses and dust-attracting objects must not be brought into contact with Styropor packaging containers. It is true that so-called "antistatic" grades of Styropor are already commercially available, but these do not exhibit the desired electrical conductivity or neutrality.

It is therefore the object of the invention to provide Styropor packaging containers which possess the desired electrical conductivity properties, the starting point being that the object of the present invention is not achieved fully if it is only the surfaces of the Styropor packaging containers which are provided with an electrically conductive layer. It is true that by using the latter method the electrical charge adhering to the surfaces of articles can be conducted away, or the accumulation of an electrostatic charge can be prevented, but what cannot be prevented is the penetration of alternating fields through the walls of the packaging material, which causes damage to delicate electronic components, for example MOS components. The prevention of these effects is only achievable if the walls of the packaging materials possess, throughout, a certain homogeneous electrical conductivity. Such a homogeneously conductive packaging article then possesses the property of also absorbing the abovementioned alternating fields and of, at the same time, destroying static fields.

According to the invention, this object is achieved by a process in which the electrically conductive foam mouldings are manufactured from polystyrene beads containing blowing agent (Styropor), which, before the final foaming process, have been treated with an aqueous plastics dispersion containing electrically conductive particles.

Styropor is a polystyrene containing blowing agent and is marketed in the form of beads or small rods. The polystyrene beads have a diameter of about 0.2 to 2.5 mm. Because of the content of blowing agent, the individual polystyrene beads expand on warming to 90°-110° C. to give closed cell particles. The cell formation is accompanied by an increase in volume which may be more than fifty times the original volume. The foaming process normally takes place in two stages. In the first stage of the foaming process, the polystyrene is prefoamed until a bead diameter of 2 to 3 mm is reached, if polystyrene beads having a diameter of about 0.5 mm are used as the starting material. In the second stage of the foaming process, the prefoamed beads are introduced into the mould and expanded, under the action of heat, until a pressure of about 1 atmosphere gauge at 105° C. is generated in the mould. In the course of this process, the individual polystyrene beads are at the same time thermoplastically welded to form the moulding.

The treatment, according to the invention, of the polystyrene beads can be carried out before the first foaming stage, but preferably after the first foaming stage, and before the second foaming stage.

The aqueous plastics dispersion, containing the electrically conductive particles, which is employed for the treatment according to the invention, should preferably conform to the following conditions:

1. During the increase in volume, it should elastically adapt to the surface of the polystyrene beads and should ensure good adhesion to the spherical surface.

2. It should not affect, or disturb, the thermoplastic welding of the individual polystyrene beads.

3. It should not be so tacky as to cause the polystyrene beads to stick together already during the treatment according to the invention.

Since the Styropor structure would be destroyed on contact with organic solvents, an aqueous plastics dispersion, which when used produces quite specific effects, is employed in accordance with the invention.

Preferably, a film-forming plastics dispersion is employed, which both possesses elastic properties and also forms intentional flaws which have the result that, on stretching, the elastic film tears open at the statistically predeterminable flaws or intended breakage points and thus forms a fine network which permits thermoplastic welding of one polystyrene bead to the next. Accordingly, the aqueous plastics dispersion is compounded so that the electrically conductive film which forms from the aqueous plastics dispersion tears open at locally confined points, when a certain extension is reached. The aqueous plastics dispersion is preferably manufactured by mixing a film-forming plastics dispersion, for example "Acronal", having an extensibiliby of 2,000%, with a non-film-forming polystyrene/carbon black dispersion, for which purpose it is possible to use, for example, about 35 parts by weight of "Styrofan" per 100 parts by weight of "Acronal". Before the polystyrene dispersion is introduced into the Acronal dispersion, the polystyrene dispersion must be mixed with a carbon black dispersion, which results in the polystyrene particles being surface-coated with conductive carbon black pigments. The tradename "Acronal" covers plastics dispersions based on acrylic esters and/or copolymers of these, whilst the trade name "Styrofan" covers plastics dispersions based on polystyrene and/or polystyrene copolymers.

The electrically conductive particles contained in the aqueous plastics dispersion may consist of carbon, for example carbon black or graphite, of noble metal or of other metals, or other non-metals, coated with noble metal. Carbon black, especially an acetylene carbon black, for example as commercially available in the form of an aqueous dispersion, is employed preferentially.

The example which follows illustrates the invention without limiting it thereto.

100 parts by weight of an aqueous 50% strength polystyrene dispersion (Styrofan 2D BASF) are introduced into 200 parts by weight of a 30% strength aqueous carbon black dispersion (Corax L). After stirring for 6 minutes, the mixture is introduced into 300 parts by weight of an aqueous 50% strength polyacrylic ester dispersion (Acronal) and the batch is stirred for 10 minutes.

The polystyrene beads, which have already been prefoamed and have a diameter of about 2 mm, are fed into a slow-running mixer, about 40 g of the above plastics dispersion being introduced for a volume of 1,000 cm3 of polystyrene beads. After about 5 minutes mixing time, all beads have been coated on the surface with the plastics dispersion. The beads, which are still moist at the surface, are dried for about 5 minutes with air warmed to 40° C.

The beads are then introduced into the metal mould, the volume introduced being so calculated as to allow the beads to expand by approximately a further 30%. The beads are then caused to expand with live steam at 105° C., until a pressure of about 1 atmosphere gauge is set up. The finished moulding is electrically conductive.

Claims (2)

What we claim is:
1. A process for making molded electrically conductive foam products which comprises heating polystyrene beads containing a blowing agent to expand the beads to form closed cell polystyrene foam particles, coating said particles by forming a mixture containing a film forming polyacrylate ester and a non-film forming polystyrene dispersion of carbon black whereby a non-continuous coating is produced, placing the partially coated particles in a mold and heating the mold's contents to about 105° C. until the prefoamed beads expand and develop a pressure of about 1 atmosphere gauge in the mold and the beads are welded together.
2. A process for making electrically conductive foam moldings which comprises mixing prefoamed polystyrene particles containing a blowing agent with an aqueous film forming polyacrylic ester dispension containing carbon black particles and expanding the resulting mixture in a mold to form a foam molding in which the said polystyrene particles are coated with electrically conductive particles and are welded together to form a foam molding.
US05/782,074 1976-04-23 1977-03-28 Electrically conductive foam mouldings Expired - Lifetime US4158031A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE2617698 1976-04-23
DE19762617698 DE2617698A1 (en) 1976-04-23 1976-04-23 Electrically conductive cellular plastic formkoerper

Publications (1)

Publication Number Publication Date
US4158031A true US4158031A (en) 1979-06-12

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Family Applications (1)

Application Number Title Priority Date Filing Date
US05/782,074 Expired - Lifetime US4158031A (en) 1976-04-23 1977-03-28 Electrically conductive foam mouldings

Country Status (3)

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US (1) US4158031A (en)
JP (1) JPS611464B2 (en)
DE (1) DE2617698A1 (en)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4301040A (en) * 1978-06-23 1981-11-17 Charleswater Products, Inc. Electrically conductive foam and method of preparation and use
DE3208485A1 (en) * 1981-03-09 1982-09-16 Yoshio Tanaka A process for the foaming of expandable resin granules
US4624865A (en) * 1984-05-21 1986-11-25 Carolina Solvents, Inc. Electrically conductive microballoons and compositions incorporating same
US4678602A (en) * 1983-05-16 1987-07-07 Daicel Chemical Industries, Ltd. Highly conductive styrenic resin composition
US4909877A (en) * 1987-01-31 1990-03-20 Kabushiki Kaisha Cubic Engineering Method for manufacturing sheet-formed buffer material using gelled material
US4931479A (en) * 1988-11-07 1990-06-05 Chomerics, Inc. Foam in place conductive polyurethane foam
US5786785A (en) * 1984-05-21 1998-07-28 Spectro Dynamics Systems, L.P. Electromagnetic radiation absorptive coating composition containing metal coated microspheres
US20050152121A1 (en) * 2003-12-19 2005-07-14 Takenori Yoshizawa Substrate accommodating tray
US20060199002A1 (en) * 2005-03-02 2006-09-07 Cabot Microelectronics Corporation Method of preparing a conductive film
US20080314619A1 (en) * 2007-06-22 2008-12-25 Samsung Electro-Mechancs Co., Ltd. Conductive paste, printed circuit board, and manufacturing method thereof
US20090030095A1 (en) * 2007-07-24 2009-01-29 Laverdure Kenneth S Polystyrene compositions and methods of making and using same
US20100200794A1 (en) * 2007-07-28 2010-08-12 Hans-Dieter Cornelius Method for producing an absorber for microwaves and absorber produced according to the method
US10597531B2 (en) * 2015-03-13 2020-03-24 Basf Se Electrically conductive particle foams based on thermoplastic elastomers

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2940260C2 (en) * 1979-10-04 1984-05-03 Metzeler Schaum Gmbh, 8940 Memmingen, De
JPS5889704A (en) * 1981-11-25 1983-05-28 Fujimori Kogyo Co Conductive bead
JPS5892540A (en) * 1981-11-30 1983-06-01 Fujimori Kogyo Kk Conductive foam molding body and manufacture therefor
JPH0311303B2 (en) * 1983-12-28 1991-02-15 Kanegafuchi Chemical Ind
JPH0461895B2 (en) * 1984-03-16 1992-10-02 Kanegafuchi Chemical Ind
JPS6232130A (en) * 1985-08-05 1987-02-12 Shinto Paint Co Ltd Expanded plastic bead
JPS6236436A (en) * 1985-08-09 1987-02-17 Shinto Paint Co Ltd Impartation of electroconductivity to expanded plastic bead
JPH02272040A (en) * 1989-04-13 1990-11-06 Tajima Kagaku Kogyo Kk Production of expansion molded body
JPH03167237A (en) * 1989-11-28 1991-07-19 Nippon Kasei Kk Production of flame-retardant polystyrene resin foam

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3154604A (en) * 1956-03-19 1964-10-27 Dow Chemical Co Method for forming articles comprising expanded thermoplastic resinous materials
US3412185A (en) * 1964-12-14 1968-11-19 Foster Grant Co Inc Method for expanding discreet articles of foamable polymeric material
US3826765A (en) * 1973-05-10 1974-07-30 Arco Polymers Inc Process of making antilumping expandable styrene polymers
US3887754A (en) * 1972-05-30 1975-06-03 Basf Ag Particulate expandable styrene polymers having desirable processing properties
US4020133A (en) * 1976-08-02 1977-04-26 Arco Polymers, Inc. Anti-lumping coating for polystyrene beads

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3154604A (en) * 1956-03-19 1964-10-27 Dow Chemical Co Method for forming articles comprising expanded thermoplastic resinous materials
US3412185A (en) * 1964-12-14 1968-11-19 Foster Grant Co Inc Method for expanding discreet articles of foamable polymeric material
US3887754A (en) * 1972-05-30 1975-06-03 Basf Ag Particulate expandable styrene polymers having desirable processing properties
US3826765A (en) * 1973-05-10 1974-07-30 Arco Polymers Inc Process of making antilumping expandable styrene polymers
US4020133A (en) * 1976-08-02 1977-04-26 Arco Polymers, Inc. Anti-lumping coating for polystyrene beads

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4301040A (en) * 1978-06-23 1981-11-17 Charleswater Products, Inc. Electrically conductive foam and method of preparation and use
DE3208485A1 (en) * 1981-03-09 1982-09-16 Yoshio Tanaka A process for the foaming of expandable resin granules
US4678602A (en) * 1983-05-16 1987-07-07 Daicel Chemical Industries, Ltd. Highly conductive styrenic resin composition
US5786785A (en) * 1984-05-21 1998-07-28 Spectro Dynamics Systems, L.P. Electromagnetic radiation absorptive coating composition containing metal coated microspheres
US4624865A (en) * 1984-05-21 1986-11-25 Carolina Solvents, Inc. Electrically conductive microballoons and compositions incorporating same
US4909877A (en) * 1987-01-31 1990-03-20 Kabushiki Kaisha Cubic Engineering Method for manufacturing sheet-formed buffer material using gelled material
US4931479A (en) * 1988-11-07 1990-06-05 Chomerics, Inc. Foam in place conductive polyurethane foam
US7579072B2 (en) * 2003-12-19 2009-08-25 Sharp Kabushiki Kaisha Substrate accommodating tray
US20050152121A1 (en) * 2003-12-19 2005-07-14 Takenori Yoshizawa Substrate accommodating tray
US7686994B2 (en) 2005-03-02 2010-03-30 Cabot Microelectronics Corporation Method of preparing a conductive film
US20060199002A1 (en) * 2005-03-02 2006-09-07 Cabot Microelectronics Corporation Method of preparing a conductive film
US20080314619A1 (en) * 2007-06-22 2008-12-25 Samsung Electro-Mechancs Co., Ltd. Conductive paste, printed circuit board, and manufacturing method thereof
US8298447B2 (en) * 2007-06-22 2012-10-30 Samsung Electro-Mechanics Co., Ltd. Conductive paste, printed circuit board, and manufacturing method thereof
US20090030095A1 (en) * 2007-07-24 2009-01-29 Laverdure Kenneth S Polystyrene compositions and methods of making and using same
US20100200794A1 (en) * 2007-07-28 2010-08-12 Hans-Dieter Cornelius Method for producing an absorber for microwaves and absorber produced according to the method
US10597531B2 (en) * 2015-03-13 2020-03-24 Basf Se Electrically conductive particle foams based on thermoplastic elastomers

Also Published As

Publication number Publication date
DE2617698A1 (en) 1977-11-10
JPS52130868A (en) 1977-11-02
JPS611464B2 (en) 1986-01-17

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